It depicts the story of what happens in Arth approximately a decade later. Over the course of more than eight years, Arthdal succeeded in suppressing the massive rebellion of the tribes slaughtered by Ta Gon in Season 1, and the Agos finally achieved the reunification of 30 clans after 200 years under the leadership of Eun Seom.
In Season 2, Ta Gon’s Kingdom of Arthdal and Eun Seom’s Ago Union are setto face an inevitable great war. Eun Seom is the ruler of the East now. Tan Ya is the successor to the Wahan clan. The story set eight years after Ta Gon has become king.
(Source: Soompi)